The research objective of this proposal is to further knowledge of the neuropharmacology of aggressive behavior. Drugs which interact with certain known neurotransmitter systems will be investigated in two animal models of aggressive behavior. The first model is attack behavior in the cat elicited by electrical stimulation of the brain. Attack may be either in the form of a "quiet biting attack" or an "affective defensive attack". The second model is shock elicited fighting in rats which is a form of "irritable" or "reactive" aggression. As an example of the applicability of this approach, previous laboratory investigations using these animal models by this investigator suggested that lithium might be a useful inhibitor of violent human aggression. This was demonstrated to be the case in a recently completed human study. Consequently, it is now of considerable interest and importance to investigate the mode of action of lithium on aggressive behavior in more detail using the animal models.